The present invention relates to a system to superpose a picture and/or a character pattern on an original facsimile pattern which is in the modulated analog signal form of amplitude modulation (AM), amplitude-phase modulation (AM-PM), frequency modulation (FM) and/or phase modulation (PM).
In a facsimile transmission system and/or a facsimile exchange system, superposition of an additional pattern on the original facsimile pattern is sometimes required. That additional pattern is, for instance, the date and/or the time that the facsimile signal is transmitted, calling subscriber recognition information, charge information, or other comments for communication purposes.
According to a prior apparatus of this kind, a modulated facsimile signal is temporarily received by a facsimile receiver, and the baseband signal in the analog form thus obtained is converted to a digital form through digital sampling process. Then the facsimile signal in the digital form thus obtained is added logically to a character signal in the digital form obtained from the control apparatus for character generation, and then the resultant logical sum is transmitted through a facsimile transmitter.
However, said prior facsimile superposition system has the disadvantages that a facsimile transmittes is necessary, thus the system structure is complicated, and further a picture quality is deteriorated since a facsimile signal is converted to a baseband signal for digital sampling.